1. Field of the Invention
The present invention relates to a method and apparatus for integrating SCUBA dive computers and air tank pressure indicators and for providing audible warnings for low tank pressures and transition into decompression zones. More particularly, it relates to aural signal generating apparatus and actuation thereof by analog gauges and computer programs.
2. Description of the Prior Art
There are numerous conditions which must be continuously and closely monitored by a SCUBA diver during a dive, including his depth, time underwater, air tank pressure, directional orientation, and, preferably, the continuous location of a dive partner. However, there are two particular conditions which can occur during a dive which are especially critical. The two conditions are low air pressure in the diver's tank and entry into a decompression zone during the dive.
Air tank pressure is most economically monitored with an analog air pressure gauge with acceptable accuracy and reliability for safety. Time and depth functions are now accurately measured by electronic dive computers which are programmed with sophisticated logic to monitor numerous parameters during a dive profile. Examples of such dive computers are disclosed in U.S. Pat. No. 4,882,678, issued Nov. 21, 1989, for a Data Sensing and Processing Device for SCUBA Divers, and U.S. Pat. No. 5,156,055, issued Oct. 20, 1992, for Ascent Rate Meter for SCUBA Divers, assigned to the assignee of the present invention. While the air pressure gauge and a dive computer are commonly arranged for carry in the same case, they have not been integrated until the present invention due to their structural incompatibility: one being mechanically driven and one being electronically actuated.
In the most ideal circumstances, the two described critical conditions would be monitored by a diver's support apparatus and automatically provide a more noticeable warning to a diver than simply the existence of a critical mark or reading on a dive gauge which is the case with either of the two types of prior art dive gauges. In an analog gauge, a pointer rotates on a dial face to point at a critical mark. In an electronic gauge, digital numbers provide a reading on the gauge face. While all dive gauges and computers are particularly directed to monitoring the two most critical conditions, there have been many attempts over time to integrate air pressure gauges and dive computers to improve the warning capability of the mechanisms, but generally they have been too expensive or for some reason unacceptable and have not improved on the basic independent apparatus.
A basic problem in attempting to provide a low air pressure warning is connected with characteristics of the analog air pressure gauge which indicates the air pressure in the diver's tank. It has proved very difficult to provide an analog gauge with an electrical signal generator indicating a preselected pressure in the tank. Expensive and complex apparatus can provide air pressure digital information which can be inputted to a computer, but that has not yet proven adaptable to SCUBA equipment. A reliable lightweight inexpensive small device is needed which will generate a signal to indicate a low pressure reading on an analog gauge. Until the present invention, this capability was not available.
A signaling means in addition to a critical mark or reading on a gauge face is also desired to provide a specialized warning in the event the diver does not observe the gauge pointing to the critical mark on the dial or a critical reading on the dive computer. Various means have been employed for this purpose, but generally they are very expensive or relatively ineffective. The present invention provides an integrated solution to these problems for both a low pressure air condition on an analog air pressure gauge or a decompression zone reading on a digital gauge. The history of the efforts to solve these problems can be traced through a representative list of prior art patents which illustrate both the difficulty in solving the problems and the present lack of a solution to the problems.
An early effort to provide an analog gauge with a warning device is disclosed in U.S. Pat. No. 4,536,756, which was issued to DePasquale, et al., as recently as 1985 and disclosed a pressure indicator and alarm for gas cylinders. That device requires a pin to be inserted through the cover of the gauge to contact the dial indicator to complete an electrical circuit. Unless the pin would bend out of the way, which is not disclosed, it cannot serve as a low pressure warning but only as an empty tank warning because the dial indicator or pointer would not otherwise be able to move past the point at which the electrical connection is established. A more sophisticated arrangement of a pressure gauge with a needle actuated electrical alarm is disclosed in U.S. Pat. No. 4,906,977 issued to Huey-Jeng more recently in 1990, but it still does not address the problems solved by the present invention.
In 1986, U.S. Pat. No. 4,613,851 was issued to Hines which disclosed a remote pressure indicating means. The indicator needle on the dial carried a permanent magnet which changed the state of reed switches to indicate different pressure levels. While it would appear that the device should function satisfactorily, it is too large, mechanically complicated, and expensive, for integration into a small dive computer and pressure gauge combination unit.
In 1989, the first combination low pressure warning device for SCUBA divers was disclosed in U.S. Pat. No. 4,800,373, issued to Mayz. It provides an audible warning as well as a visual indicator. The device uses a pressure switch in the air line to actuate the alarms and provide specialized visual indicators. This is a very expensive mechanism, but it does provide additional warnings to the critical marks or readings on a gauge. The present invention utilizes analog gauges and dive computers which have been modified to more economically provide the audible signal warning device of Mayz. Mayz does not teach a combined dive computer-low air pressure warning device as does the present invention. It therefore cannot be used to give a warning for entry into a decompression zone.
In 1992, U.S. Pat. No. 5,121,109 was issued to Murphy, Jr., et al., for an adjustable set point signaling gauge which discloses a more sophisticated mechanism for providing an electronic switch for an analog gauge. A magnet carried by the dial indicator magnetically actuates switch elements mounted at selected locations on the dial face. It is unknown whether this arrangement would work satisfactorily for a dive computer. The present invention is mechanically simpler, less expensive, and more reliable.
In 1993, U.S. Pat. No. 5,191,317 issued to Toth, et al., for a low air warning system for SCUBA divers which is particularly directed to the same problems solved by the present invention. The Toth device uses an electromagnetic transmitter positioned near the supply air tank and a corresponding electromagnetic receiver positioned on the diver's mask. This arrangement attempts to solve the problem of giving a warning to the diver apart from the air pressure gauge pointer traversing a critical mark on the gauge dial face. The low air pressure warning is a switch integrated into the air pressure line which activates the transmitter to send a visual signal to the mask. Applicant's invention provides a simpler and different warning device. Instead of a visual signal which can be lost in the confusion of the restricted view out of the mask, the present invention gives an audible warning which underwater has no other interfering sound to overcome.
In 1994, U.S. Pat. No. 5,357,242 issued to Morgano, et al., for an air pressure gauge with self-contained adjustable alarms. The device was specifically designed for diver air tank pressure monitoring and providing a warning device in addition to the gauge dial markings. While the device is designed to effect the same results as the as the present invention, it requires a mechanical connection between a shadow dial pointer and electrical contacts corresponding to the critical pressure points on the gauge dial. Mechanical electrical contacts are subject to frequent failure from several different causes, and the design of the present invention is specifically intended to overcome the problems associated therewith.
A sophisticated mechanism for providing a warning device integrated into a pressure gauge is disclosed in U.S. Pat. No. 5,051,729 issued in 1991 to Gray. That device is a pressure responsive encoder which utilizes light emitting diodes as a light source to create light signals which are transmitted by fiber-optic cables and detected by photo transistors. The light signals are reflected by an encoded rotatable disk to signal the selected pressure states of the gauge. The present invention utilizes an improved variation of the mechanical structure of this device with an improved and simplified electronic circuit to provide the results of the Mayz '373 patent.